| 1. |
- Dong, Xiao Xia, et al.
(författare)
-
Carrier-envelope-phase measurement of sub-cycle UV pulses using angular photofragment distributions
- 2022
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- Carrier-envelope-phase (CEP) of sub-cycle ultraviolet (UV) pulse strongly influences the dynamics of quantum systems, but its characterization is not accessible experimentally. Here we investigate photodissociation of a diatomic molecule from its ground-rovibrational state in a linearly polarized weak sub-cycle UV pulse with a controlled CEP. The angular distribution of photofragments shows an asymmetric profile deviating from the well-known cos(2-) or sin(2)-like ones, which can be identified as a way to imprint CEP. We unveil that such an effect stems from the temporal neighboring rotational excitation by molecular permanent dipole interaction through the joint contributions between counter-rotating and rotating terms. This in turn, opens different pathways in photodissociation dynamics. Given that the temporal excitation between various states with close energies can be manipulated by CEP of subcycle UV pulses, our results pave ways for understanding and manipulating electron, nuclear and their joint dynamics with variation of CEP of attosecond pulses.
|
|
| 2. |
- Giunta, Giovanni, et al.
(författare)
-
Optimal spatial allocation of enzymes as an investment problem
- 2022
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- Cells face various allocation problems demanding decisions on how to distribute their finite resources. They decide which enzymes to produce at what quantity, but also where to position them. Here we focus on the spatial allocation problem of arranging enzymes such as to maximize the total reaction flux produced by them in a system with given geometry and boundary conditions. We derive an optimal allocation principle demanding that the available enzymes are distributed such that the marginal flux returns at each occupied position are equal. This 'homogeneous marginal returns' (HMR) criterion corresponds to a portfolio optimization of investments that globally feed back onto all payoffs. The HMR criterion allows us to analytically understand and characterize a localization-delocalization transition in the optimal enzyme distribution. Our analysis reveals the generality of the transition, and produces a practical test for the optimality of enzyme clustering by comparing the reaction flux to the influx of substrate. Based on these results, we devise an additive construction scheme, which builds up optimal enzyme arrangements systematically rather than by trial and error. Taken together, we identify a common principle in allocation problems from biology and economics, which also serves as a design principle for synthetic biomolecular systems.
|
|
| 3. |
- Higley, Daniel J., et al.
(författare)
-
Stimulated resonant inelastic X-ray scattering in a solid
- 2022
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- When materials are exposed to X-ray pulses with sufficiently high intensity, various nonlinear effects can occur. The most fundamental one consists of stimulated electronic decays after resonant absorption of X-rays. Such stimulated decays enhance the number of emitted photons and the emission direction is confined to that of the stimulating incident photons which clone themselves in the process. Here we report the observation of stimulated resonant elastic (REXS) and inelastic (RIXS) X-ray scattering near the cobalt L3 edge in solid Co/Pd multilayer samples. We observe an enhancement of order 106 of the stimulated over the conventional spontaneous RIXS signal into the small acceptance angle of the RIXS spectrometer. We also find that in solids both stimulated REXS and RIXS spectra contain contributions from inelastic electron scattering processes, even for ultrashort 5 fs pulses. Our results reveal the potential and caveats of the development of stimulated RIXS in condensed matter.
|
|
| 4. |
- Hörnedal, Niklas, et al.
(författare)
-
Ultimate speed limits to the growth of operator complexity
- 2022
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- In an isolated system, the time evolution of a given observable in the Heisenberg picture can be efficiently represented in Krylov space. In this representation, an initial operator becomes increasingly complex as time goes by, a feature that can be quantified by the Krylov complexity. We introduce a fundamental and universal limit to the growth of the Krylov complexity by formulating a Robertson uncertainty relation, involving the Krylov complexity operator and the Liouvillian, as generator of time evolution. We further show the conditions for this bound to be saturated and illustrate its validity in paradigmatic models of quantum chaos.
|
|
| 5. |
- Löthman, Tomas, et al.
(författare)
-
Nematic superconductivity in magic-angle twisted bilayer graphene from atomistic modeling
- 2022
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- Twisted bilayer graphene (TBG) develops large moire patterns at small twist angles with flat energy bands hosting domes of superconductivity. The large system size and intricate band structure have however hampered investigations into the superconducting state. Here, using full-scale atomistic modelling with local electronic interactions, we find at and above experimentally relevant temperatures a highly inhomogeneous superconducting state with nematic ordering on both atomic and moire length scales. The nematic state has a locally anisotropic real-valued d-wave pairing, with a nematic vector winding throughout the moire pattern, and is three-fold degenerate. Although d-wave symmetric, the superconducting state has a full energy gap, which we tie to a pi-phase interlayer coupling. The superconducting nematicity is further directly detectable in the local density of states. Our results show that atomistic modeling is essential and also that very similar local interactions produce very different superconducting states in TBG and the high-temperature cuprate superconductors.
|
|
| 6. |
- Ojala, Joonas, et al.
(författare)
-
Reassigning the shapes of the 0+ states in the 186Pb nucleus
- 2022
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- Across the physics disciplines, the 186Pb nucleus is the only known system, where the two first excited states, together with the ground state, form a triplet of zero-spin states assigned with prolate, oblate and spherical shapes. Here we report on a precision measurement where the properties of collective transitions in 186Pb were determined in a simultaneous in-beam γ-ray and electron spectroscopy experiment employing the recoil-decay tagging technique. The feeding of the 02+ state and the interband 22+→21+ transition have been observed. We also present direct measurement of the energies of the electric monopole transitions from the excited 0+ states to the 0+ ground state. In contrast to the earlier understanding, the obtained reduced transition probability B(E2;21+→02+) value of 190(80) W.u., the transitional quadrupole moment ∣Qt(21+→02+)∣=7.7(33) eb and intensity balance arguments provide evidence to reassign the 02+ and 03+ states with predominantly prolate and oblate shape, respectively. Our work demonstrates a step-up in experimental sensitivity and paves the way for systematic studies of electric monopole transitions in this region. These electric monopole transitions probe the nuclear volume in a unique manner and provide unexploited input for development of the next-generation energy density functional models.
|
|
| 7. |
- Otsubo, Shun, et al.
(författare)
-
Estimating time-dependent entropy production from non-equilibrium trajectories
- 2022
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- While methods for estimating the entropy production rate of a stationary process are relatively well established, this is still a challenge in non-stationary conditions. Here, the authors propose a scheme to infer the exact value of the time-dependent entropy production rate as well as entropy production along with single realizations directly from trajectory data. The rate of entropy production provides a useful quantitative measure of a non-equilibrium system and estimating it directly from time-series data from experiments is highly desirable. Several approaches have been considered for stationary dynamics, some of which are based on a variational characterization of the entropy production rate. However, the issue of obtaining it in the case of non-stationary dynamics remains largely unexplored. Here, we solve this open problem by demonstrating that the variational approaches can be generalized to give the exact value of the entropy production rate even for non-stationary dynamics. On the basis of this result, we develop an efficient algorithm that estimates the entropy production rate continuously in time by using machine learning techniques and validate our numerical estimates using analytically tractable Langevin models in experimentally relevant parameter regimes. Our method only requires time-series data for the system of interest without any prior knowledge of the system's parameters.
|
|
| 8. |
- Panigrahi, Archisman, et al.
(författare)
-
Projected topological branes
- 2022
-
Ingår i: Communications Physics. - : Springer Nature. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- Nature harbors crystals of dimensionality (d) only up to three. Here we introduce the notion of projected topological branes (PTBs): Lower-dimensional branes embedded in higher-dimensional parent topological crystals, constructed via a geometric cut-and-project procedure on the Hilbert space of the parent lattice Hamiltonian. When such a brane is inclined at a rational or an irrational slope, either a new lattice periodicity or a quasicrystal emerges. The latter gives birth to topoquasicrystals within the landscape of PTBs. As such PTBs are shown to inherit the hallmarks, such as the bulk-boundary and bulk-dislocation correspondences, and topological invariant, of the parent topological crystals. We exemplify these outcomes by focusing on two-dimensional parent Chern insulators, leaving its signatures on projected one-dimensional (1D) topological branes in terms of localized endpoint modes, dislocation modes and the local Chern number. Finally, by stacking 1D projected Chern insulators, we showcase the imprints of three-dimensional Weyl semimetals in d = 2, namely the Fermi arc surface states and bulk chiral zeroth Landau level, responsible for the chiral anomaly. Altogether, the proposed PTBs open a realistic avenue to harness higher-dimensional (d > 3) topological phases in laboratory. Authors introduce a new class of topological materials, namely projected topological branes that are holographic images of higher-dimensional topological crystals, and feature either emergent crystalline or aperiodic quasicrystalline order. They manifest bulk-boundary and bulk-lattice defect correspondences of parent crystals and open a realistic route to harness four and higher-dimensional topological crystals in three-dimensional world.
|
|
| 9. |
- Simutis, Gediminas, et al.
(författare)
-
Single-domain stripe order in a high-temperature superconductor
- 2022
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- The coupling of spin, charge and lattice degrees of freedom results in the emergence of novel states of matter across many classes of strongly correlated electron materials. A model example is unconventional superconductivity, which is widely believed to arise from the coupling of electrons via spin excitations. In cuprate high-temperature superconductors, the interplay of charge and spin degrees of freedom is also reflected in a zoo of charge and spin-density wave orders that are intertwined with superconductivity. A key question is whether the different types of density waves merely coexist or are indeed directly coupled. Here we profit from a neutron scattering technique with superior beam-focusing that allows us to probe the subtle spin-density wave order in the prototypical high-temperature superconductor La1.88Sr0.12CuO4 under applied uniaxial pressure to demonstrate that the two density waves respond to the external tuning parameter in the same manner. Our result shows that suitable models for high-temperature superconductivity must equally account for charge and spin degrees of freedom via uniaxial charge-spin stripe fluctuations.
|
|
| 10. |
- Zhang, Wei, et al.
(författare)
-
Observation of the proton emitter 11657La59
- 2022
-
Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 5:1
-
Tidskriftsartikel (refereegranskat)abstract
- The quantum tunneling and emission of a single constituent nucleon provide a beautifully simple and unique window into the complex properties of atomic nuclei at the extreme edge of nuclear existence. In particular, for odd-odd proton emitting nuclides, the associated decay energy and partial half-life can be used to probe the correlations between the valence neutrons and protons which have been theoretically predicted to favour a new type of nuclear superfluidity, isoscalar neutron-proton pairing, for which the experimental “smoking gun" remains elusive. In the present work, proton emission from the lanthanum isotope 1165757116La59, 23 neutrons away from the only stable isotope 1395757139La82, is reported. 116La nuclei were synthesised in the fusion-evaporation reaction 58Ni(64Zn, p5n)116La and identified via their proton radioactivity using the mass spectrometer MARA (Mass Analysing Recoil Apparatus) and the silicon detectors placed at its focal plane. Comparisons of the measured proton energy (Ep = 718 ± 9 keV) and half-life (T1/2 = 50 ± 22 ms) with values calculated using the Universal Decay Law approach indicate that the proton is emitted with an orbital angular momentum l = 2 and that its emission probability is enhanced relative to its closest, less exotic, odd-even lanthanum isotope (1175757117La60) while the proton-emission Q-value is lower. We propose this to be a possible signature for the presence of strong neutron-proton pair correlations in this exotic, neutron deficient system. The observations of γ decays from isomeric states in 116La and 117La are also reported.
|
|
